The general goal of this project is to delineate the mechanisms involved in antigen recognition by and activation of thymus-independent (B) and thymus-dependent (T) lymphocytes. During the past year our efforts have concentrated on: 1) the development of new genetic models of B lymphocyte deficiency; 2) the identification and genetic mapping of B lymphocyte differentiation antigens; 3) the study of genetics of IgD and of recombination within the IgC gene complex; 4) the genetic regulation and chemical characterization of antibodies produced in response to polysaccharide haptens; 5) the regulation of antibodies and T lymphocytes capable of interacting with membrane immunoglobulin. In addition, studies of the regulation of growth of vesicular stomatitis virus in spleen cells, both in vivo and in vitro are underway.